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Infection, Pharmacology & VTE MCQs

Practice Set 17 of 68

This practice set contains high-yield board review questions covering key concepts in Infection, Pharmacology & VTE. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 321

Topic: Infection, Pharmacology & VTE
A 6-year-old African-American boy with sickle cell disease has had pain and limited use of his right arm for the past 3 days. History reveals that he sustained a humeral fracture approximately 3 years ago. A lateral radiograph is shown in Figure 25. Based on these findings, a presumptive diagnosis of chronic osteomyelitis is made. What are the two most likely organisms?
. Haemophilus influenzae and Staphylococcus aureus
. Kingella kingae and Streptococcus pneumoniae
. Staphylococcus aureus and Salmonella
. Streptococcus pneumoniae and Staphylococcus aureus
. Salmonella and Shigella

Correct Answer & Explanation

. Staphylococcus aureus and Salmonella

Explanation

DISCUSSION: The risk of Salmonella osteomyelitis is much greater in patients with sickle cell disease than the general population. The exact reason for this increased risk is still unclear, but it appears to be associated with an increased incidence of gastrointestinal microinfarcts and abscesses. Both Staphylococcus aureus and Salmonella have been mentioned as the most prevalent causative organisms. REFERENCES: Piehl FC, David RJ, Prugh SI: Osteomyelitis in sickle cell disease. J Pediatr Orthop 1993;13:225-227. Givner LB, Luddy RE, Schwartz AD: Etiology of osteomyelitis in patients with major sickle hemoglobinopathies. J Pediatr 1981;99:411-413. Epps CH Jr, Bryant DD III, Coles MJ, Castro O: Osteomyelitis in patients who have sickle-cell disease: Diagnosis and management. J Bone Joint Surg Am 1991;73:1281-1294. Lovell and Winter’s Pediatric Orthopaedics, ed 4, 1996.

Question 322

Topic: Infection, Pharmacology & VTE

An otherwise healthy 15-year-old wrestler has a 6-cm cutaneous lesion on the posterior aspect of his right elbow that he reports as a spider bite. What is the most likely diagnosis? Review Topic

. Psoriasis
. Tinea corporis
. Herpes simplex virus
. Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA)

Correct Answer & Explanation

. Psoriasis

Explanation

Patients who have skin and soft-tissue infections caused by CA-MRSA often describe the lesion as a spider bite. The cytotoxin Panton-Valentine leukocidin that is produced by many strains of CA-MRSA causes tissue necrosis, resulting in rapid development of an abscess and the appearance of a spider bite. Patients with psoriasis have thick, red skin with flaky, silver-white patches. Tinea corporis is a general term for a cutaneous fungal infection. The lesion appears as a well-demarcated erythematous plaque with a raised border and central hypopigmentation, giving it a ring-like appearance. Primary infection with herpes simplex virus can produce constitutional symptoms with burning, tingling, or stinging at the site. Grouped vesicles with clear fluid 1 to 2 mm in size form on an erythematous base and then rupture, leaving moist ulcers or crusted plaques.(SBQ07SM.48) Carbohydrate loading is a common practice among endurance athletes that works by what mechanism?Review TopicIncreasing serum fructose levelsMaximizing stored muscle glycogen for endurance after 90 minutes of exerciseDiuresisDecreasing serum glucose levelsMaximizing stored liver glycogen for endurance after 60 minutes of exerciseCarbohydrate loading is a strategy that involves changes to training and nutrition which can maximize muscle glycogen stores prior to endurance exercise lasting longer than 90 minutes.There continues to be varying scientific opinions as to whether athletes should eat low vs. high glycemic index foods, and how this will affect the amount that the serum glucose levels rise. Fructose is able to be converted to glycogen in the liver but not muscle, therefore high-fructose containing foods are suboptimal. This practice is recommended for athletes participating in events that are longer than 90 minutes (after the bodies normal supply of glycogen is depleted).Coyle et al. analyzed 10 trained cyclists who performed two bicycle ergometer exercise tests 1 wk apart. They found that blood glucose concentration was 20-40% higher during the exercise after carbohydrate ingestion than during the exercise without carbohydrate feeding. The exercise-induced decrease in plasma insulin was prevented by carbohydrate feeding. Ultimately, fatigue was postponed by carbohydrate feeding during exercise in seven out of the ten subjects.Costill et al. examined the effect of carbohydrates on muscle glycogen resynthesis in trained runners and found that muscle glycogen levels could be normalized with the proper use of carbohydrates after strenuous activity.Sherman et al. used muscle biopsies to determine the effects of moderate- or high-carbohydrate diets on muscle glycogen and performance in runners and cyclists over 7 consecutive days of training. They found that a high carbohydrate diet restored muscle glycogen to more normal levels than a moderate carbohydrate diet but did not find any difference in the effect on performance.Illustration A is a graph depicting the typical carbohydrate depletion/loading regimen that endurance athletes utilize to maximize muscle glycogen stores prior to endurance exercise. This typically involves a hard workout followed by three days of a low-carb diet, another hard workout, and another three days of a high-carb diet.Incorrect

Question 323

Topic: Infection, Pharmacology & VTE

A 53-year-old man with insulin-dependent diabetes has the ulcer on his heel shown in Figure 9. Radiographs and an MRI scan are consistent with osteomyelitis of the calcaeus, contiguous with the ulcer itself. Arterial flow to the foot is adequate. Management should consist of

. a total contact cast.
. partial calcanectomy
. Syme’s amputation
. transtibial amputation.
. nonweightbearing and IV antibiotics.

Correct Answer & Explanation

. a total contact cast.

Explanation

Smith looked at 12 pts (7 pts with DM) with a large ulcer and osteomyelitis of the calcaneus all treated with a partial calcanectomy. All pts had an ABI >.45, Transcutaneous P02 > 28mmHg, Albumin level > 3.0 and WBC > 1500. 10 of 12 healed and retained mobility. A total contact cast could be used in a pt with adequate blood flow, and no osteomyelitis A syme's amputation(through ankle) requires the use of a healthy plantar soft tissue flap for coverage . A transtibial (BKA) amputation would be the choice for a failed partial calcanectomy or in a patient who had an ABI < .45 and who wasn't a candidate for a revasculization procedure. Nonweightbearing and IV antibiotics would not be adequate in a diabetic pt with osteo of this extent.

Question 324

Topic: Infection, Pharmacology & VTE
A 6-year-old boy had a 4-day history of worsening atraumatic right thigh and knee pain. He was seen in the emergency department, where he had a temperature of 39.1°C. Laboratory studies reveal a white blood cell count of 15000 /µL. He had a small knee effusion with range of motion 0 to 90 degrees and a swollen, painful, hot distal thigh. The knee effusion was aspirated, revealing a white blood cell count of 2000 with negative gram stain. The boy was admitted to the pediatric medical service and intravenous (IV) antibiotics were initiated. The next day, MR imaging was obtained and orthopaedics was consulted. Based on Figures 8a and 8b, what is the most appropriate description of his condition?
. He has osteomyelitis with a significant subperiosteal abscess that will necessitate open drainage in the operating room.
. He has osteomyelitis without any abscess, so continued IV antibiotics and clinical observation are recommended.
. He has a muscle abscess that would best be treated by percutaneous drainage in interventional radiology.
. The MR image shows cellulitis with some adjacent myositis, so a short course of IV antibiotics followed by 2 to 3 weeks of appropriate oral antibiotics is recommended.

Correct Answer & Explanation

. He has osteomyelitis with a significant subperiosteal abscess that will necessitate open drainage in the operating room.

Explanation

The MRI scans show an advanced distal femur osteomyelitis with a substantial subperiosteal abscess. This necessitates open drainage; by definition, an abscess is avascular, so antibiotics cannot be delivered to the area without drainage.

Question 325

Topic: Infection, Pharmacology & VTE
A 7-year-old boy has had low back pain for the past 3 weeks. Radiographs reveal apparent disk space narrowing at L4-5. The patient is afebrile. Laboratory studies show a WBC count of 9,000/mm³ and a C-reactive protein level of 10 mg/L. A lumbar MRI scan confirms the loss of disk height at L4-5 and reveals a small perivertebral abscess at that level. To achieve the most rapid improvement and to lessen the chances of recurrence, management should consist of
. oral antibiotics.
. IV antibiotics.
. surgical drainage of the perivertebral abscess and IV antibiotics.
. bed rest.
. cast immobilization.

Correct Answer & Explanation

. IV antibiotics.

Explanation

DISCUSSION: The patient has diskitis. Administration of IV antibiotics speeds resolution and minimizes recurrence. Bed rest and cast immobilization have been successfully used to treat this disorder but can be associated with prolonged recovery and frequent recurrence, even when oral antibiotics are administered. A perivertebral abscess seen in association with this condition usually resolves without surgery.

Question 326

Topic: Infection, Pharmacology & VTE

A 72-year-old man was scheduled for left total knee replacement. He has a history of hypertension and deep venous thrombosis (DVT) in his right lower extremity after an ankle fracture 2 years ago that was treated nonsurgically. The patient asked about the recommended types of DVT prophylaxis or investigations. Based on the 2011 AAOS Clinical Practice Guideline, Preventing Venous Thromboembolic Disease in Patients Undergoing Elective Hip and Knee Arthroplasty , what is an acceptable option?

. Six weeks of acetylsalicylic acid postsurgically beginning the evening of surgery
. Six weeks of low-molecular-weight heparin beginning the morning after surgery
. Routine duplex scans of both lower extremities before hospital discharge to ensure the patient has not developed another DVT
. Use of pneumatic calf compressors on both lower extremities while in the hospital and 4 weeks of warfarin starting the evening of surgery

Correct Answer & Explanation

. Use of pneumatic calf compressors on both lower extremities while in the hospital and 4 weeks of warfarin starting the evening of surgery

Explanation

The 2011 AAOS guideline,Preventing Venous Thromboembolic Disease in Patients Undergoing Elective Hip and Knee Arthroplasty, recommends the combined use of mechanical and pharmacological prophylaxis in patients who have a history of previous thromboembolism. This recommendation is a consensus opinion of the work group that established these guidelines because there is no other reliable evidence for this clinical scenario. There is strong evidence against the use of routine duplex scans in patients undergoing hip and knee replacement. The remaining two responses are less appropriate because they do not include the use of mechanical prophylaxis immediately after surgery.

Question 327

Topic: Infection, Pharmacology & VTE

A 6-year-old boy is being treated for acute hematogeneous osteomyelitis of the distal femur with intravenous antibiotics. The best method to determine the success or failure of initial treatment is by serial evaluations of which of the following studies? Review Topic

. Radiographs
. MRI
. Erythrocyte sedimentation rate (ESR)
. CBC with differential
. C-reactive protein (CRP)

Correct Answer & Explanation

. Radiographs

Explanation

Successful antibiotic treatment of acute osteomyelitis should lead to a rapid decline in the CRP. The CRP is the most sensitive study to follow the treatment of osteomyelitis. The CRP should decline after 48 to 72 hours of appropriate treatment. CBC and ESR are helpful in initial evaluation and diagnosis, but remain abnormal in the early phase of treatment regardless of response. Imaging studies are useful for surgical planning or secondarily if the CRP remains elevated.

Question 328

Topic: Infection, Pharmacology & VTE

A 42-year-old woman underwent an instrumented posterior spinal fusion at L3-S1 with transforaminal lumbar interbody fusion. She had an excellent

. Observation
. Oral antibiotics only
. IV antibiotics only
. Irrigation and debridement of the surgical site
. Irrigation and debridement of the surgical site with hardware removal

Correct Answer & Explanation

. Observation

Explanation

The MRI scans reveal a postoperative infection. Observation and antibiotics are not appropriate choices. There is a large fluid collection and this requires decompression because the patient has neurologic changes. There is considerable debate regarding the removal of hardware. Many contend that biofilm on the implants can harbor the infection. However, these complications usually can be treated with serial irrigations, debridements, and IV antibiotics. The incidence of infection has been widely studied with varying rates in fusions with instrumentation. Rates appear to be increased with instrumentation, yet these infections usually can be managed without hardware removal.

Question 329

Topic: Infection, Pharmacology & VTE

A 30-year-old patient has had severe left hip pain and difficulty ambulating, necessitating the use of a cane, for the past 6 months. A photomicrograph of the femoral head sectioned at the time of surgery is shown in Figure 31. What is the most likely diagnosis?

. Renal osteodystrophy
. Pyogenic osteomyelitis
. Osteoarthritis
. Osteonecrosis
. Tuberculosis osteomyelitis

Correct Answer & Explanation

. Renal osteodystrophy

Explanation

DISCUSSION: The photomicrograph demonstrates a wedge-shaped infarct with femoral head collapse; therefore, the diagnosis is osteonecrosis of the femoral head.  Perthes disease and osteoarthritis do not involve a wedge-shaped defect.  Tuberculosis of the hip joint results in greater destruction of the articular cartilage.REFERENCES: Basset LW, Mirra JM, Cracchiolo A III: Ischemic necrosis of the femoral head: Correlation between magnetic resonance imaging and histologic sections.  Clin Orthop 1987;223:181-187.Sugano N: Osteonecrosis, in Fitzgerald RH, Kaufer H, Malkani AL (eds): Orthopedics.  St Louis, MO, Mosby, 2002, pp 878-887.

Question 330

Topic: Infection, Pharmacology & VTE

A 3-year-old child has refused to walk for the past 2 days. Examination in the emergency department reveals a temperature of 102.2 degrees F (39 degrees C) and limited range of motion of the left hip. An AP pelvic radiograph is normal. Laboratory studies show a WBC count of 9,000/mm P 3 P , an erythrocyte sedimentation rate (ESR) of 65 mm/h, and a C-reactive protein level of 10.5 mg/L (normal < 0.4). What is the next most appropriate step in management?

. Technetium Tc 99m bone scan
. Intravenous antibiotics
. Oral antibiotics
. CT of the hips
. Aspiration of the left hip

Correct Answer & Explanation

. Technetium Tc 99m bone scan

Explanation

DISCUSSION: Examination reveals an irritable hip, creating a differential diagnosis of transient synovitis versus pyogenic hip arthritis.  Kocher and associates described four criteria to help predict the presence of infection: inability to bear weight, fever, ESR of more than 40 mm/h, and a peripheral WBC count of more than 12,000/mmP3P.  This patient meets three of the four criteria, with a positive predictive value of 73% to 93% for joint infection.  Therefore, aspiration of the hip is warranted, with a high likelihood that emergent hip arthrotomy will be indicated.  Ideally, intravenous antibiotics should be administered after culture material has been obtained from needle aspiration of the hip.  An urgent bone scan is better indicated as a screening test for sacroiliitis or diskitis.  If the arthrocentesis proves negative, CT or MRI of the pelvis may be indicated to rule out a pelvic or psoas abscess.REFERENCES: Del Beccaro MA, Champoux AN, Bockers T, et al: Septic arthritis versus transient synovitis of the hip: The value of screening laboratory tests.  Ann Emerg Med 1992;21:1418-1422.Kocher MS, Mandiga R, Zurakowski D, et al: Validation of a clinical prediction rule for the differentiation between septic arthritis and transient synovitis of the hip in children.  J Bone Joint Surg Am 2004;86:1629-1635.Kocher MS, Zurakowski D, Kasser JR: Differentiating between septic arthritis and transient synovitis of the hip in children: An evidence-based clinical prediction algorithm.  J Bone Joint Surg Am 1999;81:1662-1670.

Question 331

Topic: Infection, Pharmacology & VTE

A 6-year-old boy is being treated for acute hematogeneous osteomyelitis of the distal femur with intravenous antibiotics. The best method to determine the success or failure of initial treatment is by serial evaluations of which of the following studies?

. Radiographs
. MRI
. Erythrocyte sedimentation rate (ESR)
. CBC with differential
. C-reactive protein (CRP)

Correct Answer & Explanation

. Radiographs

Explanation

DISCUSSION: Successful antibiotic treatment of acute osteomyelitis should lead to a rapid decline in the CRP. The CRP is the most sensitive study to follow the treatment of osteomyelitis. The CRP should decline after 48 to 72 hours of appropriate treatment. CBC and ESR are helpful in initial evaluation and diagnosis, but remain abnormal in the early phase of treatment regardless of response. Imaging studies are useful for surgical planning or secondarily if the CRP remains elevated.REFERENCES: Unkila-Kallio L. Kallio MJ, Eskola J, et al: Serum C-reactive protein, erythrocyte sedimentation rate, and white blood cell count in acute hematogenous osteomyelitis of children. Pediatrics 1994;93:59-62.Herring JA(ed): Tachdjian’s Pediatric Orthopaedics, ed 4. Philadelphia. PA. WB Saunders, 2008, pp 2090-2100.AL-Madena Copy

Question 332

Topic: Infection, Pharmacology & VTE

Hip pain of month duration has developed in a year-old man with a previous total hip arthroplasty. He underwent dental work 6 weeks ago. Aspiration shows a white blood cell count of more than 6,000 cells/μL (reference range 4,500 to 11,000 cells/μL) and the presence of gram-positive cocci in clusters on Gram stain. The orthopaedic surgeon recommends urgent debridement and irrigation. Fixation of the components is judged to be stable, and the surgeon elects to retain the implants. The patient has a final culture that reveals methicillin-resistant Staphylococcus  aureus (MRSA). If the attending physician recommends the two-stage protocol, including the use of an antibiotic-cement spacer, what is the most likely prognosis for this patient?

. Better functional outcome than that associated with infections from sensitive organisms
. Same functional outcome as that associated with infections from sensitive organisms
. Same prognosis for eradication of infection as that associated with infections from sensitive organisms
. Poorer prognosis for eradication of infection than that associated with infection from sensitive organisms

Correct Answer & Explanation

. Better functional outcome than that associated with infections from sensitive organisms

Explanation

DISCUSSION:The patient has a late infection of at least 4 weeks symptomatic duration that most likely is hematogenous in etiology. This infection is not an acute hematogenous infection that can successfully be treated with irrigation and debridement. Retention of the  implants with debridement and irrigation alone has been associated with a poor prognosis. In a recent study, the success rate was only 44% in a series of 104 patients at a mean 5.7-year follow-up. In one study of 50 infections attributable to MRSA or methicillin- resistantStaphylococcus epidermidisorganisms treated with a two-stage protocol, the failure rate was21%. Patients who experienced successful infection treatment had lower functional outcome measures using the Western Ontario and McMaster Universities Osteoarthritis Index, the University of CaliforniaLos Angeles Activity Score, and the 12-item Oxford Knee Score, however.

Question 333

Topic: Infection, Pharmacology & VTE

A man who weighs 75 kg (165 pounds) is scheduled for elective total hip arthroplasty. He reports a history consistent with anaphylaxis from penicillin. Within 1 hour of the incision the patient should receive 1000 mg of

. cefazolin.
. cefuroxime.
. vancomycin.
. clindamycin.

Correct Answer & Explanation

. cefazolin.

Explanation

The recommended antimicrobial prophylaxis for total hip arthroplasty is cefazolin or cefuroxime unless the patient has an allergy to beta-lactam antibiotics. Patients with an allergy should be given vancomycin 10 to 15 mg/kg or clindamycin 600 to 900 mg. Because this patient has an allergy to penicillin, he should be given 1000 mg of vancomycin within 1 hour of the skin incision.

Question 334

Topic: Infection, Pharmacology & VTE

Acetaminophen is an antipyretic medication. It exerts its pharmacologic effects by inhibiting which of the following enzymes?

. Cyclooxygenase-2 (COX-2)
. Interleukin-1 beta (IL-1 β)
. Tumor necrosis factor alpha (TNF-α)
. Hydroxytryptamine (5-HT)
. Metalloproteinases (MMPs)

Correct Answer & Explanation

. Cyclooxygenase-2 (COX-2)

Explanation

DISCUSSION: Acetaminophen inhibits prostaglandin E2 production via IL-1 β, without affecting cyclooxygenase-2 enzymatic activity.  The therapeutic concentrations of acetaminophen induce an inhibition of IL-1 β-dependent NF-kappa β nuclear translocation.  The selectivity of this effect suggests the existence of an acetaminophen-specific activity at the transcriptional level that may be one of the mechanisms through which the drug exerts its pharmacologic effects.  Acetaminophen does not affect any of the other enzymes named above.REFERENCE: Mancini F, Landolfi C, Muzio M, et al: Acetaminophen down-regulates interleukin-1beta-induced nuclear factor-kappaB nuclear translocation in a human astrocytic cell line.  Neurosci Lett 2003;353:79-82.

Question 335

Topic: Infection, Pharmacology & VTE

Which of the following studies is considered most sensitive in monitoring a therapeutic response in acute hematogenous osteomyelitis?

. Blood culture
. WBC count
. Erythrocyte sedimentation rate (ESR)
. C-reactive protein
. Radiography

Correct Answer & Explanation

. Blood culture

Explanation

DISCUSSION: C-reactive protein declines rapidly as the clinical picture improves.  Failure of the C-reactive protein to decline after 48 to 72 hours of treatment should indicate that treatment may need to be altered.  Blood culture is positive only 50% of the time and will be negative soon after antibiotics are administered, even if treatment is not progressing satisfactorily.  WBC count is highly variable and poorly correlated with treatment.  The ESR rises rapidly but declines too slowly to guide treatment.  Radiographic findings may not change but can take up to 2 weeks to show changes.REFERENCE: Unidia-Kallio L, et al:  Serum c-reactive protein, ESR and WBC in acute hematogenous osteomyelitis in children.  Pediatrics 1994;93:59-62.

Question 336

Topic: Infection, Pharmacology & VTE

A 3-year-old girl has had wrist pain, a fever, and has refused to move her right wrist for the past 10 days. She has an oral temperature of 102 degrees F (38.7 degree C). Laboratory studies show an erythrocyte sedimentation rate of 50 mm/h, a WBC count of 11,000/mm 3 , and a left shift. AP and lateral radiographs are shown in Figures 57a and 57b. What is the most likely diagnosis?

. Leukemia
. Eosinophilic granuloma
. Acute osteomyelitis
. Ewing’s sarcoma
. Nonossifying fibroma

Correct Answer & Explanation

. Leukemia

Explanation

DISCUSSION: The most likely diagnosis is acute osteomyelitis.  She may also have a septic wrist; however, the lytic lesion in the distal radius has the typical presentation and radiographic appearance of metaphyseal osteomyelitis.  In this area of sluggish vascular flow, low oxygen tension, and low pH, bacterial seeding is common and is the usual origin of metaphyseal osteomyelitis.  Leukemia and Ewing’s sarcoma can present as a lytic lesion with an elevated erythrocyte sedimentation rate, but they are much less common than osteomyelitis and are less focal and more destructive in appearance.  Nonossifying fibroma is typically metaphyseal and eccentric; however, it is well circumscribed and uncommon in the upper extremity.  Eosinophilic granuloma does not typically present with inflammatory indicies.REFERENCES: Dormans JP, Drummond DS: Pediatric hematogenous osteomyelitis: New trends in presentation, diagnosis and treatment.  J Am Acad Orthop Surg 1994;2:333-341.Song KM, Sloboda JF: Acute hematogenous osteomyelitis in children.  J Am Acad Orthop Surg 2001;9:166-175.

Question 337

Topic: Infection, Pharmacology & VTE

A 34-year-old man sustained a gunshot wound to the knee 18 months ago and was treated with bullet removal and a 10 day course of oral antibiotics. He now complains of 12 months duration of pain in the thigh and recent ulceration and drainage of the skin near the site of his gunshot wound. Physical exam is notable for a draining sinus tract, erythema and tenderness of the mid-thigh. He is afebrile. An MRI image of this patient is shown in Figure A. Which of the following is the most appropriate management?

. Two week course of oral cephalosporin
. Core needle bone culture followed by intravenous antibiotics
. Surgical debridement, culture, and intravenous antibiotics
. Core needle biopsy, chest CT scan, and bone scan
. Neoadjuvant chemotherapy and wide resection followed by adjuvant chemotherapy

Correct Answer & Explanation

. Two week course of oral cephalosporin

Explanation

The clinical presentation and radiographs are consistent with chronic osteomyelitis. The MRI shows chronic changes of the distal femur with intraarticular (knee) extension. Chronic osteomyelitis is notable for a sequestrum, which is necrotic bone that has become avascular and no longer connected to the normal bone via the Haversian canal system. Involucrum refers to the new bone forming around the sequestrum. Often the involucrum will form a sinus tract allowing the sequestrum to drain into the soft tissues. Illustration A is a diagram of chronic osteomyelitis depicting the sequestrum (E), Involucrum (C), and sinus tract (D). In contrast to acute osteomyelitis, chronic osteomyelitis is often not eradicated with intravenous antibiotics alone. All necrotic bone (including the sequestrum) must be resected as it serves as a nidus for infection. Antibiotics should be guided off culture sampling of the infection.In the referenced article by Parsons and Strauss, the management of chronic osteomyelitis is reviewed.OrthoCash 2020

Question 338

Topic: Infection, Pharmacology & VTE
  • An otherwise healthy 65-year-old man has had chronic pain in his prosthetic knee for the past 9 months. Repeated aspirations reveal a coagulase-negative staphylococcus infection. To eradicate the infection while maintaining the best possible joint function, management should consist of
. Long-term administration of IV and oral antibiotics
. Open soft-tissue debridement, retention of prosthetic components, and IV antibiotics
. Immediate exchange arthroplasty with antibiotic-impregnated cement
. Two-stage surgical prosthetic exchange and IV antibiotics
. Resection arthroplasty and IV antibiotics

Correct Answer & Explanation

. Long-term administration of IV and oral antibiotics

Explanation

Postoperative wound infections following total joint arthroplasty are generally classified as acute or chronic. The time period is either 2 or 4 weeks from the time of implantation depending on whom you read. This will, generally, determine if you can attempt a one-stage procedure. The other considerations are the bacteria’s resistance to antibiotics and whether or not it produces glycocalyx. If the microorganism elaborates glycocalyx it is highly likely that it will remain after surgical removal of the implants and debridement of the joint.Present recommendations are to avoid a one-stage reconstruction in a patient in whom a glycocalyx elaborating microorganism has been isolated. In one study 52% of the isolates of S. epidermidis and 28% of the isolates of S. aureus elaborated glycocalyx. The microbiology laboratory can be asked to determine if the microorganisms elaborate glycocalyx. In the present case it should be assumed that the staphylococci elaborate glycocalyx and are resistant to antibiotics. A two-stage procedure is indicated for these reasons alone.Antibiotic therapy alone has been used for a select group of patients who could not medically tolerate either a one-stage or a two-stage arthroplasty. The patient in this case is listed as otherwise healthy.The decision to perform a resection arthroplasty as a definitive procedure without reimplantation is based on the bacteria’s resistance to antibiotics, quality of the local soft tissues, the complexity of the reconstruction, the patient’s refusal to have another operation, the patient’s overall health, or a combination of these factors. None of which appear to be present in this case.

Question 339

Topic: Infection, Pharmacology & VTE

The parents of a previously healthy 3-year-old child report that she refused to walk on awakening. Examination later in the day reveals that the patient can walk but with a noticeable limp. She has a temperature of 99.5 degrees F (37.5 degrees C). Range of motion measurements are shown in Figure 50. An AP pelvis radiograph is normal. Laboratory studies show a WBC count of 9,000/mm 3 and an erythrocyte sedimentation rate of 10 mm/h. Management should consist of

. observation.
. technetium Tc 99m bone scan.
. MRI of the pelvis.
. aspiration of the hip joint.
. IV antibiotics.

Correct Answer & Explanation

. observation.

Explanation

DISCUSSION: The patient has the typical history and presentation of transient synovitis of the hip, a condition that is more common in children age 2 to 5 years but which may affect children up to 12 years.  The discomfort typically is noted on awakening, and the child will refuse to walk.  Later in the day, the pain commonly improves and the child can walk but will have a limp.  Mild to moderate restriction of hip abduction is the most sensitive range-of-motion restriction.  The extent of the evaluation for transient synovitis depends on the intensity and duration of symptoms.  Because she has been afebrile for the past 24 hours, observation is the management of choice.  In the differential diagnosis of suspected transient synovitis, septic arthritis of the hip is the primary disorder to exclude.  Osteomyelitis of the proximal femur also should be considered.  In most patients, clinical examination will differentiate of these disorders to a reasonable certainty.  Plain radiographs are normal in the early stage of an infectious process.  Ultrasonography shows increased fluid in the hip joint in both transient synovitis and septic arthritis.  MRI can differentiate the two conditions; however, this test would require general anesthesia and is not required in most patients in this age group.  If a child with transient synovitis has a concurrent infectious process such as an upper respiratory tract infection or otitis media, the temperature will most likely be elevated.  In this situation, a full evaluation for an infectious process and initiation of IV antibiotics should be considered.  This would include radiographs, CBC count, erythrocyte sedimentation rate, blood cultures, aspiration of the hip joint, and IV antibiotics.REFERENCES: Del Beccaro MA, Champoux AN, Bockers T, Mendelman PM: Septic arthritis versus transient synovitis of the hip: The value of screening laboratory tests.  Annals Emerg Med 1992;21:1418-1422.Kehl DK: Developmental coxa vara, transient synovitis, and idiopathic chondrolysis of the hip, in Morrissy RT, Weinstein SL (eds): Lovell and Winter’s Pediatric Orthopaedics, ed 5.  Philadelphia, PA, Lippincott Williams and Wilkins, 2001, pp 1035-1058.

Question 340

Topic: Infection, Pharmacology & VTE
Figure below shows the abdominal radiograph obtained from a 70-year-old woman who experiences nausea and abdominal tightness 48 hours following left total knee arthroplasty performed under general anesthesia. She received 24 hours of cefazolin antibiotic prophylaxis and a patient-controlled analgesia narcotic pump for pain management. She has been receiving warfarin for thromboembolic prophylaxis. Her severe abdominal distension and markedly decreased bowel sounds are most likely secondary to the administration of
. general anesthesia.
. antibiotics.
. warfarin.
. narcotics.

Correct Answer & Explanation

. narcotics.

Explanation

DISCUSSION: The radiograph reveals severe intestinal dilatation, which has occurred as the result of acute colonic pseudo-obstruction and is associated with excessive narcotic administration following total joint arthroplasty. Anesthetic type, antibiotic administration, and warfarin have not been associated with this obstruction. Electrolyte imbalances such as hypokalemia have been associated with postsurgical acute colonic pseudo-obstruction.

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